Date of Award

2024

Document Type

Honors Thesis (Open Access)

Department

Colby College. Biology Dept.

Advisor(s)

Susan Childers

Second Advisor

Ron Peck

Third Advisor

Yee Mon Thu

Abstract

A selenate respiring bacterium, Dechloromonas sp. A34, was isolated from a seleniferous mining site in southeastern Idaho. A34 was of interest due to its ability to respire up to 20 mM selenate, the highest concentration tested. The strain has been proposed to represent a new species of bacteria within the Dechloromonas genera, with the prospective name Dechloromonas selenatirespirans (manuscript in preparation). Our research presents characterization of a putative periplasmic binding protein found within an operon that contains genes encoding a putative selenate reductase. The gene, named serX (selenate reductase gene X), is 855 base pairs and encodes a putative protein 284 aa in length. Sequence analysis shows it is homologous to phosphonate and arsenite periplasmic binding proteins found within other microorganisms. We conducted amino acid sequence analysis which supports the theory that SerX is secreted into the periplasm and acts as a selenate binding protein. We created a deletion mutant of serX by replacing a portion of the sequence with a gene encoding tetracycline resistance (tet) that will help to clarify the role of SerX in selenate respiration. A methodology was developed to assess the impact of SerX on selenate reduction in E. coli heterologously expressing a selenate reductase and identified a toxic effect of SerX expression within the bacterium. With environmental selenium contamination due to mining, agriculture, and industrial practices on the rise, studying a protein involved in processing selenate could contribute greatly to bioremediation technologies being developed to counter selenium pollution.

Keywords

Microbiology, anaerobe, selenium, periplasm, respiration

Download

Available for download on Saturday, May 23, 2026

Share

COinS